4.
Monitor the "BRAKE LAMP SWITCH" parameter on the scantool.
The brake light switch indicates brake pedal status to the ABS control unit. The switch is turned on when brake is depressed. The brake light switch is a normally-open contact which runs to battery voltage when active (brake depressed).
The brake light signal is a reference to judge driver's intention for braking and The HECU checks open or short circuit of brake light switch for normal ABS/ESP control. If an error is present, the warning lamp will illuminate.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● Voltage monitoring | ● Open circuit in brake switch line ● Faulty brake light switch | |
Case 1 | Monitoring Period | ● Continuous (only no under voltage is not detected) | |
Enable Conditions | ● If the BLS-signals is high for 60 s at following condition.
| ||
Case 2 | Monitoring Period | ● Continuous (only normal voltage) | |
Enable Conditions | ● For redundancy reasons an additional BLSpVor-signal is created by the pressure sensor signal. If the pressure sensor is compensated, the threshold for generating the BLSpVor signal is 10 bar. If the pressure sensor is not compensated, the threshold is increased by 15bar. If this signal is set without any hardware-BLS-signals and if no pomp is operated during that time, a fault is set after the braking. ● If the pressure signal is higher than 80bar and not both of the hardware-BLS are set, a fault is stored after 1s. | ||
Fail Safe | ● Inhibit the ESP control and ABS/EBD control is available. ● The ESP warning lamps are activated. | ||
Brake Light Switch | Voltage Range of "High" | Voltage Range of "Low" |
above 4.5V | 0V ~ 2V |
Connect scantool to Data Link Connector(DLC).
Ignition "ON" ＆ Engine "OFF"
Press the brake pedal.
Monitor the "BRAKE LAMP SWITCH" parameter on the scantool.
Whenever brake pedal is pushed down, is the brake switch's scantool data changed ON/OFF?
▶ Fault is intermittent caused by poor connection in brake light switch line and/or HECU's connector or was repaired and HECU memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
▶ Go to "Terminal and Connector Inspection" procedure.
Many malfunctions in the electrical system are caused poor harness(es) and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and then go to "Verification Of Vehicle Repair" procedure.
▶ Go to "Signal Circuit Inspection" procedure.
Ignition "ON" ＆ Engine "OFF".
Don't press the brake pedal.
Measure voltage between the terminal "30" of the HECU harness connector and chassis ground.
Specification : Brake Light Switch - Approx. 0 V
Is the measured voltage within specifications?
▶ Go to "Signal Circuit Inspection (brake pedal is depressed)" procedure.
▶ Check for open or blown 15A fuse referring to "Circuit Diagram".
▶ Check for open or short to battery between the battery terminal(+) and the terminal "30" of the HECU harness connector. Repair as necessary and then go to "Verification of vehicle Repair" procedure. If OK, Go to "Component Inspection" Precedure.
Ignition "ON" ＆ Engine "OFF".
Press the brake pedal.
Measure voltage between the terminal "30" of the HECU harness connector and chassis ground.
Specification : Brake Light Switch - Approx. B+
Is the measured voltage within specifications?
▶ Fault is intermittent caused by open or short harness in brake light switch, faulty brake light switch or was repaired and HECU memory was not cleared. Go to "Verification Of Vehicle Repair" procedure.
▶ Check for open or short to ground between the battery terminal(+) and the terminal "30" of the HECU harness connector. Repair as necessary and then go to "Verification Of Vehicle Repair" procedure.
▶ If OK, Go to "Component Inspection" Precedure.
Ignition "OFF".
Disconnect brake switch connector.
Measure resistance between the terminal "1", "2" of the brake switch.
Specification :
Resistance between the terminal "1, 2" of the brake switch - ∞Ω (when the plunger is pushed down), 0Ω (when the plunger isn't pushed down).
Is the measured voltage within specifications?
▶ Fault is intermittent caused by open or short harness in brake light switch, faulty brake light switch. Go to "Verification Of Vehicle Repair" procedure.
▶ Substitute with a known-good brake light switch and check for proper operation. If problem is corrected, replace brake light switch and then go to "Verification Of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Connect scantool and select "Diagnostic Trouble Codes (DTCs)" mode
Using a scantool, Clear DTC.
Operate the vehicle within DTC Detecting Condition in General Information
Are any DTCs present?
▶ Go to the applicable troubleshooting procedure.
▶ System performing to specification at this time.
